**4. Applications of composites**

Biomass residues generated from agro-businesses gained much attention as reinforcement of various polymeric materials due to their inherited properties (i.e., biodegradability and renewability, etc.) and low-cost production. In addition, the consciousness about conservation of the environment has forced the industrial and scientific communities to look for an alternative for the agro-business generated waste. Several biomass residues (i.e., rice husks, maize stalks and sugarcane bagasse) were successfully incorporated into different polymers to improve their mechanical and physical properties. Herein we will discuss the application of sugarcane bagasse as reinforcing filler for various polymeric materials. Different forms of fillers can be generated/produced from sugarcane bagasse waste which include sugarcane bagasse ashes (SBA), fibers (SB), nanocrystals (CNCs), cellulose and micro/nanofibers (MFC or CNF) were incorporated in various polymer matrices such as polypropylene (PP) [28], low density polyethylene (LDPE) [29] polyethylene oxide (PEO) [30], nylon [31] as well as thermosets [32, 33].

### **4.1. Composites processing**

It is recognized that the processing technique plays major role on the dispersion of the fillers in the polymer composite materials. There are three widely used methods which include melt compounding, *in situ* polymerization and solution casting. It is of interest to mention that the size of the filler also plays a significant role on the dispersion especially with regard to their processing technique. In most cases micro-fillers (fibers) are preferably prepared *via* melt compounding which is the most conducive method with regard to industrial scale-up process. On the other hand, the nanostructured sugar bagasse-based fillers (e.g., CNCs) are preferably prepared *via in situ* or solution casting which are known to improve their dispersion because these filler are mostly obtained in a solution form which controls their processability. This in turn have forced most of the fabrication methods to concentrate on keeping the dispersed state of the fillers in the solution by adopting either the solution processing technique or polymerization in the presence on the nanostructured fillers.

#### *4.1.1. Melt compounding*

Melt compounding is the most preferable processing technique for industrial scale-up. This technique is usually suitable for highly hydrophobic polymers which normally lead to inhomogeneity of the resulting composite materials. The functionalization/chemical modification of the fillers and/or polymer can be applied to overcome the agglomeration in order to achieve durable and desired properties [14, 34]. The alkali pre-treatment of sugarcane bagasse is often applied to increase roughness of the fibers by removing some of the wax and non-cellulosic substances. It was reported that this kind of treatment was not suitable to improve the interaction/adhesion and dispersion of the fibers for highly hydrophobic polymer matrices which causes detrimental effect on the properties of the resulting composite material [35].

Compression molding was also used to prepare the SB-based composites [36]. This method, however, resulted in blisters, weak interfacial adhesion and inhomogeneous fiber distribution, regardless of the fiber retreatment.

Melt extrusion followed by melt compression of SB/HDPE composites was studied by Mulinari et al. [37]. The SB cellulose was extracted using sulfuric acid in a reactor followed by surface modification using zirconium oxychloride (ZrOCl<sup>2</sup> ·8H2 O). In another studies, they used thermokinetic mixer followed by compression molding [17, 38]. The modification using ZrOCl<sup>2</sup> ·8H2 O reduced the extent of agglomeration in the composite materials. Moreover, the adhesion between the cellulose and HDPE was improved by surface modification. It was concluded that these processing methods are applicable to produce composites materials using hydrophobic polymers such as HDPE and PP. It worth mentioning that these melt processing methods did not have a significant influence on the extent of the dispersion of the fillers as well as their adhesion. As far as the modification of the filler surface is concerned, it can be concluded that regardless of the type/structure (form) of filler the surface modification can improve the dispersion and adhesion for improved properties.

#### *4.1.2. In situ processing*

changes in the combustion temperatures as it can be obtained at burning temperatures rang-

Biomass residues generated from agro-businesses gained much attention as reinforcement of various polymeric materials due to their inherited properties (i.e., biodegradability and renewability, etc.) and low-cost production. In addition, the consciousness about conservation of the environment has forced the industrial and scientific communities to look for an alternative for the agro-business generated waste. Several biomass residues (i.e., rice husks, maize stalks and sugarcane bagasse) were successfully incorporated into different polymers to improve their mechanical and physical properties. Herein we will discuss the application of sugarcane bagasse as reinforcing filler for various polymeric materials. Different forms of fillers can be generated/produced from sugarcane bagasse waste which include sugarcane bagasse ashes (SBA), fibers (SB), nanocrystals (CNCs), cellulose and micro/nanofibers (MFC or CNF) were incorporated in various polymer matrices such as polypropylene (PP) [28], low density polyethylene (LDPE) [29] polyethylene oxide (PEO) [30], nylon [31] as well as thermosets [32, 33].

It is recognized that the processing technique plays major role on the dispersion of the fillers in the polymer composite materials. There are three widely used methods which include melt compounding, *in situ* polymerization and solution casting. It is of interest to mention that the size of the filler also plays a significant role on the dispersion especially with regard to their processing technique. In most cases micro-fillers (fibers) are preferably prepared *via* melt compounding which is the most conducive method with regard to industrial scale-up process. On the other hand, the nanostructured sugar bagasse-based fillers (e.g., CNCs) are preferably prepared *via in situ* or solution casting which are known to improve their dispersion because these filler are mostly obtained in a solution form which controls their processability. This in turn have forced most of the fabrication methods to concentrate on keeping the dispersed state of the fillers in the solution by adopting either the solution processing technique

Melt compounding is the most preferable processing technique for industrial scale-up. This technique is usually suitable for highly hydrophobic polymers which normally lead to inhomogeneity of the resulting composite materials. The functionalization/chemical modification of the fillers and/or polymer can be applied to overcome the agglomeration in order to achieve durable and desired properties [14, 34]. The alkali pre-treatment of sugarcane bagasse is often applied to increase roughness of the fibers by removing some of the wax and non-cellulosic substances. It was reported that this kind of treatment was not suitable to improve the interaction/adhesion

or polymerization in the presence on the nanostructured fillers.

ing between 400 and 500°C.

230 Sugarcane - Technology and Research

**4.1. Composites processing**

*4.1.1. Melt compounding*

**4. Applications of composites**

The addition of the filler into the precursor (polymer monomer) increases the possibility of good dispersion and interaction between the polymer and filler. Motaung et al. [31] prepared CNC/nylon nanocomposites *via in situ* polymerization. The CNC were added into hexamethylenediamine (i.e., nylon monomer) followed by sonication to enhance the dispersion of the CNCs. Nevertheless, the content of the filler played a major role on the dispersion as well as adhesion. Despite the better dispersion obtained under this processing method, for CNCbased composites this scenario can cause a detrimental effect on the resulting properties of the composite materials. The interwhiskers network formed between the nanocrystals is important to achieve desired properties in CNC/polymer nanocomposites [39, 40].

### *4.1.3. Solution casting*

Sugarcane bagasse is currently used as a one of the sources of the cellulose nanocrystals (CNCs) for the reinforcing polymers. In these studies the state of dispersion of the CNC in water was maintained by adopting the solution casting method [41, 42]. In this method the nanocrystals are mixed with the polymers in a suitable solvent and allow the solvent to evaporate. Uniform distribution of the nanocrystals within the polymeric material was obtained which can lead to other physical and/or chemical properties. It is also essential to take into account the amount of the nanocrystals incorporated into the polymeric material since the higher the content may result in the agglomeration of the nanocrystals which could cause detrimental effect on the intended application or desired properties [42]. Similar preparation method was utilized in the preparation of SB fibers composites especially for polymers which are soluble in water [30].

#### *4.1.4. Other processing methods*

Thermosets polymer composites are usually prepared by curing at a temperature depending on the resin-type. The casting of the constituent of the composites onto the steel mold followed by compression molding under certain conditions (pressure, time and/or temperature) influence the properties of the resulting composite material [43–45]. de Sousa et al. [43] studied the effect of pressure on the pre-treated chopped SB-polyester composites. They reported that the combination of all other parameters such as size of the filler, pre-treatment and pressure exerted during molding can be optimized to obtain the desired properties. It is interesting to note that the thermosets have an edge over other polymers due to the fact that it can offer high filler loadings (>65–80 wt%). In addition, the processing temperature is lower when compared to melt mixing and the easy processability. The disadvantage of these composites is that they are not recyclable, and the highly possible alternative is to use them as polymeric fillers or for heat generation. Nevertheless, there has been paradigm shift from synthetic polyesters to a new class of biodegradable resins to overcome the recycling issues [45].

Most of the SB polymer composites are prepared through melt compounding, thus is often based on the hydrophobic thermoplastics. This results in reduction of the mechanical properties of the resulting composite materials due to lack of adhesion as well as inhomogeneous fiber distribution [36, 37]. Chemical treatment can be utilized to improve the distribution as well as interaction/ adhesion between highly hydrophilic SB fibers and hydrophobic thermoplastics [37]. Similarly, the sugarcane bagasse ashes (SBA)-based composites are prepared *via* melt mixing with an additional treatment being applied on either polymeric matrix or ashes to improve the mechanical properties [1, 46]. Since silica has been used as reinforcement of rubbers, the high content of silica in the SBA opens their applicability in rubber composites. Dos Santos et al. [47] reinforced natural rubber with SBA and found that the strong interfacial interaction between the SBA and rubber improved the mechanical properties. A recent study based on the comparison between the commercial silica and SBA reported that it is possible to replace the commercial silica with SBA as rubber reinforcing filler [48]. It was found that the replacement of commercial silica with

SBA did not influence the mechanical properties of the composite materials that much.

fibers compared to other with glass transition (T<sup>g</sup>

by increase in Tg

the pith/PVC composites.

The effect of NaOH treatment on the SB for the polyester composites was found to be improving the adhesion between the composites' components [45]. The alkali treatment led to finer fibers due to dissolution of the hemicellulose which increased the aspect ratio. A maximum improvement with only 1% NaOH was obtained with 13% in tensile strength, 14% in flexural strength and 13% in impact strength compared to untreated composites. This resulted in better interfacial adhesion between the polyester and NaOH-treated fibers. Other surface treatment of the SB fibers utilized as reinforcement of the thermosets were also studied to improve the interfacial adhesion between the fibers and the polymeric matrix [32, 49]. Despite the general observation of the mechanical properties which increases linearly with increase in fiber content some of these treatment significantly improves the overall performance of the thermosets composites [32, 49]. Vilay et al. [49] pre-treated the SB fibers with NaOH followed by acrylic acid (AA). They reported that the AA treatment improved the tensile strength, Young' modulus, flexural strength, and flexural modulus of the composites when compared to the untreated and NaOH-treated fibers. The elastic modulus was also increased for the treated

be due to the enhanced interfacial adhesion between the polymer and the filler as confirmed

A rind and pith component of the SB-based unsaturated polyesters composites was investigated [50]. The flexural strength and flexural modulus were found to increase with fiber content for pith and rind fibers; and impact strength showed similar behavior. The tensile properties were also increased as compared to the unfilled polymeric material. It was, however, found that the rind outperform pith based composites. This was related to the structural difference between the pith and rind. The pith consists of big hollow cavities called lumen reducing bulk density of the fiber and acts as acoustic and thermal insulators. On the other hand, the rind have small size lumens and many finer cellulose fibers. Similar study was conducted elsewhere using poly (vinyl chloride) as matrix [11]. It was also reported that the rind/ PVC displayed superior properties (i.e., flexural strength and modulus) when compared to

justify the restriction of polymer chains movement by the reinforcing filler.

) shifting to higher temperatures. This could

Sugarcane Bagasse and Cellulose Polymer Composites http://dx.doi.org/10.5772/intechopen.71497 233
